WASHINGTON – Six Air France flights between Paris and Los Angeles were abruptly grounded yesterday due to “credible” information that several terrorist passengers were planning to turn the planes into deadly fireballs.

The unprecedented axing of Christmas Eve and Christmas Day flights over growing fears of new terror hijackings came after U.S. officials in Paris demanded the French government ground the planes – at least some of which were jumbo 747s.

American authorities notified France that “two or three” suspicious people, possibly Tunisian nationals, intended to board the flights from Paris, said a spokesman for French Prime Minister Jean-Pierre Raffarin.

The names of the Tunisians apparently appeared on both a U.S. watch list of possible terrorists and a list of passengers booking Air France flights to Los Angeles. Before the cancellations were announced, no one with those names went through airport security checks yesterday and there have been no arrests, officials said.

One U.S. official, who spoke on condition of anonymity, said the U.S. government had been trying to keep the negotiations with France confidential, “hoping that we would be able to lure some of these people in.”

A French TV station reported the terrorists were members of Osama bin Laden’s al Qaeda terror group.

The Department of Homeland Security called the danger a “credible threat.”

Brain Doyle, a spokesman for the Transportation Security Administration, said Homeland Security Director Tom Ridge had personally been in contact with the French over the terror plot. He declined to offer any specifics or say whether other countries were involved.

A senior U.S. government official insisted it was France’s decision to halt the flights.

But the spokesman for Raffarin said Washington had threatened to refuse the planes permission to land in the United States if France let them leave Europe.

Three of the flights were scheduled to depart yesterday – two from Paris and one from Los Angeles. Air France gave the flight numbers as 68, 69 and 70.

The three other flights were scheduled to leave today – two from Los Angeles and one from Paris. Air France listed those flight numbers as 68, 69 and 71.

The cancellations came almost exactly two years after “shoe bomber” Richard Reid was arrested on an American Airlines flight from Paris to Miami. He was sentenced to life in prison for his attempt at igniting a bomb in his shoe.

The Air France cancellations occurred two days after the White House raised the national threat level from “yellow” to “orange,” a sign that the possibility of terrorists launching an attack has risen to “high.”

Most of the threats have centered on bin Laden and the fear that he or his allies would use a foreign flight as a new vehicle for a 9/11-like attack.

Among the warnings gleaned by U.S. officials this week is the possibility that bin Laden or al Qaeda operatives would use air-cargo planes or passenger airlines as missiles and that the flight crews might include undercover terrorists.

Concern about possible threats spread to La Guardia Airport last night when flights were halted after a woman set off alarms at a security check in the Delta terminal and then ran off.

Also, the federal government imposed a flight restriction over downtown Chicago at the request of city officials.

Continuing investigation: The U.S. government is comparing data it had compiled on passengers preparing to board flights entering the United States, as well as data on the flight crews on those flights, with terrorist watch lists it has compiled.